For the Smart Grid, a ‘Synchrophasor’
By MATTHEW L. WALD
Move over, smart meter — and make room for the synchrophasor.
It might sound sound like a device out of a Start Trek movie, but a synchrophasors is actually a metal box about the size of a mailbox (this kind) that sits in an electricity substation — the junction point for transmission lines. It measures conditions on those lines — like power flows, voltage and some more exotic characteristics of electricity, like frequency and phase angle — and reports the information back to a computer at a grid control center.
The hope is that synchrophasors, when deployed by the hundreds, will increase the amount of energy that can be reliably transmitted on the high-voltage grid, which will be necessary if North America is to integrate more wind and solar power.
Of course, much of this sort of monitoring is already commonly done. The difference is, most existing devices report once every two to four seconds, which is an eternity in the world of the high voltage grid. The synchrophasors will report back 30 times a second.
Better yet, it will report back with a time stamp, which it will generate by listening for a GPS signal, so that all the reports can be synchronized and computers at the control center can be clear on the sequence of events. Hence the term “synchrophasor.”
With more frequent sampling, grid operators will be able to see disturbances as they begin to develop, and take compensating actions, like shifting the location where power is being added to the system, according to Roger Harszy, the vice president of real time operations at the Midwest Independent Transmission System Operator, the largest grid organization in North America in terms of square miles covered — and the second largest in terms of customers supplied.
The Midwest I.T.S.O. said earlier this week that it had received a promise of $17.3 million from the Energy Department to pay for half of a $34 million program to install 150 to 200 of the devices.
(Synchrophasors cost only $2,000 to $3,000 each, but connecting them and building a computer system to handle the data is more expensive.)
The Energy Department is using Recovery Act money to seed synchrophasor projects around the country. It said last November that it was giving the Western Interconnection, which covers the area from the Rockies to the Pacific, $53.9 million for the devices. Several dozen are in service now but the long-term plan is four thousands of synchrophasors spread around the United States and Canada.
When deployed, they will be a bit like traffic cameras at major intersections, allowing controllers to get a sense of the overall system. For the Midwest I.T.S.O., this is a step up from the situation in the summer of 2003, when major transmission lines in the system were out of service, and operators did not know it. The result was a massive blackout.
If there is a blackout, synchrophasors could also determine which failures came first, and which were merely effects of the first failures. Establishing the sequence of events was a nightmare for the investigators in the 2003 blackout, because while individual parts that shut down — like circuit breakers — had individual data loggers, the clocks on them were not coordinated, making it hard to establish where the disturbance began.
But engineers hope the main use of synchrophasors will be preventive, not forensic. “Bringing in this type of technology, the speed of the data coming in will give our operators the ability to see issues emerging,’’ said Mr. Harszy.
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